Magnetron amplifier



MAGNETRON AMPLIFIER Filed Nov. 9, 1953 IA it I INVENTOR g/JAELEIF ML/T7'0/V ATTO R N EY United States Patent MAGNETRON AMPLIFIER Charles V.Litton, Redwood City, Calif., assignor to Litton Industries, Inc.

Application November 9, 1953, Serial No. 390,971

3 Claims. (Cl. 31539) This invention relates to magnetrons, and moreparticularly to magnetrons in which energy may be injected foramplification or control purposes.

Magnetron oscillators, amplifiers or modulators have been proposed inthe past for which external energy, to be amplified or to control thefrequency of the magnetron, is introduced from some external source intothe resonators of the magnetron. This is generally accomplished byinserting a loop or probe into the resonator at some point adjacent theouter wall of the magnetron. The coupling at this point however, is in ahigh energy field within the resonator and in a portion thereof which ispredominantly inductive. Accordingly, these coupling circuits have thedraw-back that there is a considerable back-coupling of energy from theresonator to the coupled line. This may be minimised to some extent byimpedance control but is difficult to reduce the back-coupling to avalue lower than 10% of the energy generated in the magnetron.

It is an object of this invention to provide an energy input couplingarrangement for magnetrons wherein the energy may be supplied to themagnetron by a coupling unit which is relatively free from thisundesired backcoupling effect.

According to a feature of this invention there is provided a couplingmeans which may extend through the wall in the partition separating theresonators of a multiresonator magnetron, into a point substantiallyflush with the inner edge of this partition wall. The energy thus isintroduced at a low energy point of the normal magnetron operation andis, therefore, substantially free from the back-coupling effects oftenencountered.

The above-mentioned and other features and objects of this inventionwill become more apparent and the invention itself will be bestunderstood by reference to the following description of an embodiment ofthe invention taken in conjunction with the accompanying drawings, inwhich:

Figure l is a sectional view of a magnetron structure embodying theprinciple of this invention.

Figure 2 is a fragmentary view of Fig. 1 taken along the line 2-2 ofFig. 1, and

Figure 3 is a fragmentary portion of a magnetron illustrating thealternative coupling arrangement in accordance with this invention.

In Fig. I there is shown a magnetron anode 1 having a body portion 2 anda plurality of partitioning walls or vanes 3 forming a plurality ofindividual resonators. The usual cathode 4 may be provided centrally ofthese resonators. The energy output coupling is illustrated at 5 and maycomprise a wave guide with an impedance matching ramp 6 and a sealedwindow 7.

The input energy, controlling the magnetron, may be applied to a specialcoupling means 8 illustrated in Figs. 1 and 2 as a coaxial lineconsisting of an outer conductor formed by the wall of an opening 9 inone of the vanes 3. An inner conductor 10 is l .ounted within thisopening 9 and spaced from the wall. The inner end ll of conductor 16 mayterminate substantially flush with the inner end of the partitioningwall 3. In order to complete the input coupling an outer conductorextension 12 may be brazed or otherwise secured to the outer surface of.the magnetron body 2 and this may be sealedto the inner conductor 9 bymeans of a glass bead'13.' The energy input coupling may then consist ofa coaxial line coupler 14 which may be coupled to conductors 9 and 13 asillustrated.

It will be apparent that if energy supplied over coupler 8 is of thesame frequency as the normal operating frequency of the magnetron, aneffective amplification to this energy may be achieved. If some otherfrequency is used a heating effect may be produced within the magnetronserving to vary the tuning of the magnetron. This may be usedselectively to control the outer frequency of the magnetron for a givenfrequency value or may be used to produce a frequency modulated outputfrom the magnetron as a whole.

It will be noted that the input energy is coupled only at the point ofspacing between the inner end of conductor 10 and the inner edge of vane3. Accordingly, energy is introduced at a point where relatively little,if any, back coupling can occur.

In Fig. 3 is illustrated a fragmentary portion of a magnetron anodeillustrating an alternative method of input energy coupling. In thisview the magnetron anode body 15 is shown as a different form ofmulti-cavity resonator in which substantially circular resonators areformed as indicated at 16. The partitioning wall then is the portion 17of the magnetron body 15 intermediate adjacent cavities 16. Inpartitioning wall 17 is provided an opening 18 extending from the inneredge thereof to the external surface of the magnetron 15. Opening 18 isdimensioned as a wave guide of suitable value to carry the energy usedto modify the magnetron operation. This wave guide formed by opening 18may be coupled through any desired means such as the born 19 to anexternal wave guide 20. Closure of the magnetron may be effected bymeans of an insulating window 21 as shown.

It will be understood that the particular type of input coupling lead isnot dependent upon the type of multiresonator magnetron used.Accordingly other of the couplers shown in Figs. 1 and 3 may readily beinterchanged so far as their use with the particular form of magnetronis concerned.

Furthermore, it is clear that if desired an open twoconductor line couldbe connected to the coupling means 8 of Fig. 1 instead of the coaxialinput line 14 illustrated.

While I have described above the principles of this invention inconnection with specific apparatus, it is to be clearly understood thatthis description is made only by way of example and not as a limitationto the scope of the invention, as set forth in the objects thereof andin the accompanying claims.

What is claimed is:

1. A magnetron comprising an anode having a body portion and a pluralityof inwardly extending radial partition .walls forming a plurality ofresonators, a cathode positioned near the inner ends of said partitionwalls, and a coupling means for introducing energy into said magnetronto modify the energy developed in said resonators comprising an openingextending from one end through one of said partition walls to theexternal surface of said anode, the walls of said opening being formedby said one partition wall whereby the only energy transfer opening intosaid magnetron is at the inner end of said one partition wall.

2. A magnetron according to claim 1, wherein said coupling means furthercomprises a-conductor positioned concentrically of said opening andterminating at its inner end substantially at the inner end of said onepartition Wall, forming a coaxial input coupler with the walls of saidopening.

3. A coupler according to claim 1, further comprising 2,473,828 SpencerJune 21', 1949 4 Stinchfield Apr. 8, 1952 Tonks et a1 Nov. 10, 1953Kroger June 26, 1956 g. If

